Skip to main content

Full text of "The manufacture and properties of iron and steel"

See other formats

results obtained by E. A. Ouster at The Baldwin Locomotive Works. In the case of the slow speed there is less difference between the two determinations of the elastic limit than is shown by Henning, while with the fast speed there is more. The influence of the pulling speed upon the recorded physical properties is considered in the next section.
Parallel Determinations of the Elastic Limit by the Autographic Device and by the Drop of the Beam.*
No. of tests.	Pulling speed.	Ultimate strength ; pounds per sq. in.	Elastic limit; pounds per square in. as determined by		Elastic ratio; per ce.nt., as determined by	
			Autographic device.	Fall of beam.	Autographic device.	Fall of beam.
6 8	1 inch in 8 minutes. 4 inches in 1 minute.	66820 58870	86120 85890	87510 40580	68.6 61.0	66.0 68.8
The determination of the elastic limit was discussed in The Engineering News, of July 25, 1895. After reviewing the arguments presented by several engineers, the following conclusions were reached:
"Having shown the impossibility of determining, by micrometric measurement, the elastic limit, when it is defined as the point at which the rate of stretch begins to change, and the extreme variability of the position of the so-called 'yield-point' with the method of running the machine and with the method of measuring and recording results, had we not better drop these new definitions and methods of attempting to locate points whose position is so extremely variable, and whose determination depends so largely upon the personal equation of the observer, and return to the good, old-fashioned definitions and methods? If, for scientific purposes, there is any need for determining microscopically that point at which the rate of stretch begins microscopically to change, let us call that point the 'limit of proportionality/ as Bauschinger did, and leave its determination to the college professors.
"Let us keep the old term elastic limit with its old significance as that point at which a permanent set visible to tbe naked eye takes place, at which the rate of stretch increases so that the in-
* From E. A. Ouster, Baldwin Locomotive Works, Philadelphia, Pa.